implement a couple fixme's by implementing __extension__ properly.


git-svn-id: https://llvm.org/svn/llvm-project/cfe/trunk@57806 91177308-0d34-0410-b5e6-96231b3b80d8
diff --git a/lib/Parse/ExtensionRAIIObject.h b/lib/Parse/ExtensionRAIIObject.h
new file mode 100644
index 0000000..e7d4446
--- /dev/null
+++ b/lib/Parse/ExtensionRAIIObject.h
@@ -0,0 +1,42 @@
+//===--- ExtensionRAIIObject.h - Use RAII for __extension__ -----*- C++ -*-===//
+//
+//                     The LLVM Compiler Infrastructure
+//
+// This file is distributed under the University of Illinois Open Source
+// License. See LICENSE.TXT for details.
+//
+//===----------------------------------------------------------------------===//
+//
+//  This file defines and implements the ExtensionRAIIObject class.
+//
+//===----------------------------------------------------------------------===//
+
+#ifndef LLVM_CLANG_PARSE_EXTENSION_RAII_OBJECT_H
+#define LLVM_CLANG_PARSE_EXTENSION_RAII_OBJECT_H
+
+#include "clang/Basic/Diagnostic.h"
+
+namespace clang {
+
+  /// ExtensionRAIIObject - This saves the state of extension warnings when
+  /// constructed and disables them.  When destructed, it restores them back to
+  /// the way they used to be.  This is used to handle __extension__ in the
+  /// parser.
+  class ExtensionRAIIObject {
+    void operator=(const ExtensionRAIIObject &);     // DO NOT IMPLEMENT
+    ExtensionRAIIObject(const ExtensionRAIIObject&); // DO NOT IMPLEMENT
+    Diagnostic &Diags;
+    bool OldState;
+  public:
+    ExtensionRAIIObject(Diagnostic &diags) : Diags(diags) {
+      OldState = Diags.getWarnOnExtensions();
+      Diags.setWarnOnExtensions(false);
+    }
+    
+    ~ExtensionRAIIObject() {
+      Diags.setWarnOnExtensions(OldState);
+    }
+  };
+}
+
+#endif